The invention relates to a coffee machine of the type having a brewing means which contains a brewing chamber limited by a circumferential wall, in which a piston movable to and fro is disposed and whose one side has an opening, a closing element being movable relative to the brewing chamber via a gear which releases the opening for apportioning coffee powder in a first position and closes it in a second position and a stripper moving across the opening for ejecting the used up coffee grounds in the case of a raised piston.
Such a coffee machine is known from DE-OS 29 12 841. The known coffee machine has an upright, prismatic brewing chamber, at whose upper front side an opening is provided for filling in the coffee powder and for ejecting the used up coffee grounds. A piston moves up and down in the brewing chamber, which is displaced in one of its positions that far upwardly that its piston surface is in alignment with the upper edge of the brewing chamber. A closing element designed as a further piston is provided for closing the opening of the brewing chamber, which is movable from its position closing the opening at first vertically upwardly and then that much horizontally alongside of the brewing chamber that the opening is open towards above. A feed receptacle is provided for apportioning coffee powder, which can be moved in horizontal direction that much above the brewing chamber that coffee powder falls into the brewing chamber through an opening. After completion of the apportioning process, the feed receptacle is again moved alongside the brewing chamber. A stripper for stripping off and ejecting the used up coffee grounds is disposed at the edge of the feed receptacle leading upon the movement of the feed receptacle into its apportioning position. After the completion of a preceding brewing process or prior to the beginning of a new brewing process, the closing element is thus at first moved upwardly and then to the side so that the opening of the brewing chamber is open. Then the piston in the brewing chamber moves that much upwardly until its piston surface is in the plane of the opening, the used up coffee grounds thus project from the opening.
Then the feed receptacle with the leading stripper moves across the opening, the stripper pushing the used up coffee grounds to the opposite side of the brewing chamber. The piston in the brewing chamber moves again downwardly so that now the coffee powder for the new brewing process can be apportioned After the completion of the apportioning process the feed receptacle moves again into its starting position; however, the stripper is then also returned over the opening of the brewing chamber. During this return, the stripper of the known coffee machine is to clean once again the upper part of the brewing chamber. However, since this movement is effected in a direction opposite to the first cleaning movement, the used up coffee grounds possibly still located on the edge of the opening are pushed towards the inside and fall onto the new coffee powder in the brewing chamber. The stripper moves moreover over the opening in the further course of its movement so that coffee grounds adhering to it may also fall into the brewing chamber filled with new coffee powder. Coffee grounds residues in the brewing chamber, however, can negatively influence the quality of the coffee brewed subsequently. The known coffee machine is moreover relatively complex due to the plurality of its moving elements and consequently also subject to more sources of failures. The linear movements of the feed receptacle must e.g. be exactly coordinated with the L-shaped movements (with vertical and horizontal components) of the closing element.